• Korean Journal of Materials Research
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• v.19 no.1
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• pp.28-32
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• 2009

Silicon carbide (SiC) is a promising material for power device applications due to its wide band gap (3.26 eV for 4H-SiC), high critical electric field and excellent thermal conductivity. The Schottky barrier diode is the representative high-power device that is currently available commercially. A field plate edge-terminated 4H-SiC was fabricated using a lift-off process for opening the Schottky contacts. In this case, Ni/Ti dual-metal contacts were unintentionally formed at the edge of the Schottky contacts and resulted in the degradation of the electrical properties of the diodes. The breakdown voltage and Schottky barrier height (SBH, ${\Phi}_B$) was 107 V and 0.67 eV, respectively. To form homogeneous single-metal Ni/4H-SiC Schottky contacts, a deposition and etching method was employed, and the electrical properties of the diodes were improved. The modified SBDs showed enhanced electrical properties, as witnessed by a breakdown voltage of 635 V, a Schottky barrier height of ${\Phi}_B$=1.48 eV, an ideality factor of n=1.04 (close to one), a forward voltage drop of $V_F$=1.6 V, a specific on resistance of $R_{on}=2.1m{\Omega}-cm^2$ and a power loss of $P_L=79.6Wcm^{-2}$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.2
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• pp.151-156
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• 2009

The stomach contents of Lumpenella longirostris, Malacocottus gibber and Bothrocara hollandi from the East Sea were examined to determine their feeding ecology. Specimens were caught seasonally from 2004 to 2006. The primary prey items of each species included crustaceans and mollusks. L. longirostris is a benthophage that primarily consumes bottom crustaceans and bivalves. M. gibber and B. hollandi are meso-pelagicphages that primarily consume amphipods and cephalopods. However, the species are opportunistic feeders that exploit the available prey in their habitat. The empty stomach ratio of the species is larger than that of offshore species (e.g. hairtail fish and yellow goose fish), and the prey diversity of the species evaluated in this study was much smaller than that of offshore species.

• Korean Journal of Microbiology
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• v.36 no.2
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• pp.112-118
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• 2000

A new gene encoding an acidophilic TEX>$\alpha$-amylase of Bacillus cil-culans KCTC3004 was cloned into Eschericlzia coli using pUC19 as a vector. The gene localized in the 5.8 kb PstI DNA fragment was expressed independently of its orientation in the cloning vector showing enzyme activity about 40 times greater than that produced by the original B, circulans The optimum pH and temperature of the cloned enzyme were pH 3.6 and 45^{\circ}C.$ respectively. The enzyme hydrolyzed starch to produce maltotriose and maltooligosaccharides. The SDS-PAGE and zymopram of the enzyme produced in E coli(p.4L850) indicated a molecular weight of 55,000.

• Journal of the Korean Society of Food Culture
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• v.30 no.6
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• pp.790-796
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• 2015

The objective of this study was to investigate the physicochemical properties and antioxidant activities of seven (A, B, C, D, E, F, G) commercial ketchups marketed in Korea. The 70% ethanol extracts were prepared and evaluated for total phenolic content, DPPH and ABTS radical scavenging activities, and metal chelating effect. pH ranged from 3.64 to 3.94, and soluble solid and reducing sugar contents of samples were 2.21~3.51oBrix and 4.78~13.45%, respectively. Salinity of samples was in the range of 1.79 to 3.21%, and sample G showed the lowest salinity. The lightness, redness, and yellowness of the Hunter color system of samples were 15.42~19.94, 18.55~23.98, and 20.87~24.34, respectively. The phenolic contents ranged from 1.37 to 2.60 mg GAE (gallic acid equivalents)/g, with samples F and G exhibiting the highest contents. Antioxidant activity determined based on DPPH and ABTS radical scavenging activities, and metal chelating effects were 45.10~90.87, 55.35~92.53, and 71.10~92.20%, respectively, at a concentration of 200 mg/mL. Samples A and G showed higher antioxidant activity than other samples. There were positive correlations between phenolic contents and antioxidant activity, suggesting that phenolic compounds are the major contributors to antioxidant activity.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.303-306
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• 2004

참멍게의 체액세포로부터 산추출 후, 조 추출물에서 천연항균소재를 개발하기 위해 먼저 멍게 조 추출액을 직접 Tricine-SDS PAGE를 통하여 주요 펩타이드들의 분자량의 범위를 살펴본 결과 6kDa 이하의 분자량의 펩타이드들이 다량 존재함을 알수 있었다. 펩타이드들의 size별 항균활성을 알아보기 위해 여러 사이즈의(100, 50, 30, 10 kDa)의 한외여과만으로 여과하여 그 여과액들의 specific 활성을 알아본 결과 여과막의 cut-off size에 상관없이 거의 인정한 specific activity를 가짐을 알 수 있었다. 멍게 조 추출액의 여러 미생물에 대한 항균 스펙트럼을 알아보기 위해 E.coli, P. aeruginosa, S. typhi, V. parahaemolyticus, L. monocytogenes, B. sutillus, S. aureus, S. mutans 균주들을 $10^5 CFU/ml$로 부터 4log 감소시키는 농도를 측정한 결과 각각 200, 50, 60, 10, 25, 30, 100, 100ppm 농도였으며, 대표적 상용화 항균 펩타이드인 Nisin과의 항균활성 비교 결과 비슷하거나 월등히 뛰어난 결과를 보여주었다. 또한 추출액의 열안정성을 측정하기 위해 $100^{\circ}C$에서 10분간 가열한 후 원액과의 항균력의 차이를 Radial diffusion assay로 알아본 결과 항균력의 차이가 거의 없음을 알 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.25 no.2
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• pp.49-55
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• 2006

Measurement of impact sound insulation of floor, by current Korean Standard KS F 2810-2. is to be made with peak levels over 4 point in a receiving room. But it is often the case that there is inconsistency in results at various receiving points in the receiving room. Such variations obviously have effects on the repeatability and reproducibility of measured data. The result shows that there are even 10 dB deviations in 63Hz octave band frequency range and relatively less variations are occurred in other low frequency ranges. Such variations seems to be coming from modal overlaps of the receiving room. According to current rating method of floor impact sound. KS F 2863-2, that may affect on the single number latins scheme. From the result of tests in this study, there are 2dB to 6dB differences in the sin91e number with the combination of measurement points. This means that the reduction of measurement variations from the microphone positions is needed for a better credibility of measurement results.

• Journal of Environmental Science International
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• v.3 no.3
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• pp.253-261
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• 1994

Chloroform present in the swimming water disinfected with sodium hypochlorite is released to the air of swimming pools. The air chloroform concentrations were measured in two swimming pools A and B which applied both sodium hypochlorite a:d ozone. Thew mean concentrations are 28.0 $\mu\textrm{g}$/m3 and 33.6 $\mu\textrm{g}$/m3in the swimming pools A and B, respectively. On the other hand, the mean water chloroform concentrations in the swimming pools A and B were 23.9 $\mu\textrm{g}$/l and 19.5 $\mu\textrm{g}$/l, respectively. The air chloroform concentrations were lower in the swimming Bools A and B than those reported by previous studies abroad employed the swimming pools which applied sodium hypochlorite only for water disinfection. The water chloroform concentrations were also lower in this study than in the previous studies. The relationship between the air and water chloroform concentrations measured in this study was significant with p=0.002 and Rz=0.42. At similar time to the indoor air sampling, outdoor air samples were collected at two sites near each of the swimming Pools A and B. The mean outdoor air chloroform concentrations near the swiminE Pools A and B were 0.41 $\mu\textrm{g}$/m3 and 0.16 $\mu\textrm{g}$/m3, respectively. The outdoor air chloroform concentrations measured in this study were equal to or lower than those reported by previous studies abroad. 'rho chloroform dose inhaled for a typical one-hour swim was estimated to be 25.9 $\mu\textrm{g}$ per person, corresponding to a specific 0.37 $\mu\textrm{g}$/kg body weight for a reference 70 Kg male adult, while the inhalation dose of chloroform from the outdoor air was estimated to be 5.6 $\mu\textrm{g}$ per person per day, corresponding to a specific 0.08 $\mu\textrm{g}$/Kg/day for the same reference male adult.

• Journal of Food Hygiene and Safety
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• v.35 no.4
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• pp.375-381
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• 2020

This study assessed the contamination levels of total aerobic bacteria, fungi, coliforms, Escherichia coli, Bacillus cereus, and Staphylococcus aureus and qualitative analysis of Salmonella spp. and Listeria monocytogens in six raw materials (beef, bean sprout, Chinese cabbage, king oyster mushroom, Korean cabbage, and sweet pumpkin) of home meal replacement (HMR) Shabu-Shabu meal kit distributed in markets. The total aerobic bacteria, fungi, and coliforms were detected as 3.98-6.50, 2.78-3.52, and 2.02-3.28 log CFU/g, respectively. Especially, beef was highly contaminated with total aerobic bacteria (6.50 log CFU/g) and coliforms (3.28 log CFU/g). Over 5 log CFU/g of total aerobic bacteria were also detected in bean sprout, Chinese cabbage, and sweet pumpkin. Less than < 2 log CFU/g of coliforms were detected in all vegetables. E. coli was not detected in any of the six samples (ND: < 1 log CFU/g). S. aureus was detected as 1.33-1.71 log CFU/g in most samples but it was not detected in beef and Korean cabbage. B. cereus was assessed as 1.15-2.01 log CFU/g in most samples but it was not detected in Korean cabbage. L. monocytogenes was qualitatively detected as 25-50% in most samples except for king oyster mushroom. Salmonella spp. were not qualitatively detected in any of the six samples. The microbial contamination levels determined in the current study may be potentially used as the basic data to execute microbial risk assessments of HMR foods such as Shabu-Shabu meal kit.

• Journal of Microbiology and Biotechnology
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• v.17 no.4
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• pp.638-643
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• 2007

The full encoding sequence for human type II hexokinase (HXK II) was cloned into the E. coli expression vector pET 21b and expressed as a C-terminally hexahistidine-tagged protein in the BL2l (DE3) strain. The IPTG-induced HXK II approximately accounted for 17% of the total E. coli proteins, and 81% of HXK $II_{6{\times}His}$ existed in inclusion bodies. To improve the production of soluble recombinant HXK II protein, in the functionally active form, we used low temperature, and the osmotic stress expression method. When expressed at $18^{\circ}C$, about 83% of HXK $II_{6{\times}His}$ existed in the soluble fraction, which amounted to a 4.1-fold yield over that expressed at $37^{\circ}C$. The soluble form of HXK $II_{6{\times}His}$ was also highly produced in the presence of 1M sorbitol under the standard condition $(37^{\circ}C)$, which indicated that temperature downshift and low water potentials were required to improve the yield of active recombinant HXK II protein. The expressed protein was purified by metal chelate affinity chromatography performed in an IDA Excellose column charged with $Ni^{2+}$ ions, resulting in about 40mg recombinant HXK II protein obtained with purity over 89% from 51 of E. coli culture. The identity of HXK $II_{6{\times}His}$ was confirmed by Western blotting analysis. Taken together, using the stress-governed expression described in this study, human active HXK II can be purified in sufficient amounts for biochemical and biomedical studies.

• Journal of Sericultural and Entomological Science
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• v.53 no.2
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• pp.135-142
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• 2015

The American cockroaches, Periplaneta americana L. was the most important worldwide pest species. It has been an public health problems. We were determinated life cycle and extraction of crude extracts by chemical reagents from cockraches (P. americana L.). The extracted crude solution has been antibacterial activity to gram negative bacteria (Pseudomonas aeruginosa, $6.44{\pm}1.03mm$), gram positive bacteria (Bacillus subtilis, $1.88{\pm}0.40mm$), and fungus (Candida albicans, $5.61{\pm}0.57mm$) using radial diffusion assay. We were analysed of up-regulation of Glutathione-S-transferases (GSTs) stimulation, indicating that antioxidantial protein from various classes are simultaneously expressed in a single insect upon infection or injury. The gene from Periplaneta americana L. were cloned, analysed sequence, and measured protein expression by Real Time PCR (Polymerase Chain Reaction).